1. Field of the Invention
The present invention relates to a cleaning method for a turbo molecular pump, and in particular to a cleaning method for a turbo molecular pump connected to a processing chamber of a substrate processing apparatus.
2. Description of the Related Art
Conventionally, substrate processing apparatuses that carry out predetermined processing on substrates such as wafers for semiconductor devices have a processing chamber (hereinafter referred to merely as the “chamber”) in which a substrate is housed and subjected to predetermined processing. In such a substrate processing apparatus, a highly-reactive gas is usually introduced as a processing gas into the chamber. If the highly-reactive gas remains in the chamber, when the chamber communicates with another chamber, the highly-reactive gas remaining in the chamber may diffuse into the other chamber and cause a trouble. Moreover, in the chamber, particles arising from deposit attached to an inner wall of the chamber and reaction product produced during predetermined processing are floating. If these floating particles become attached to surfaces of substrates, a short circuit will occur in products such as semiconductor devices manufactured from the substrates, resulting in the yield of the semiconductor devices decreasing. To remove the highly-reactive gas and the particles from the chamber, the substrate processing apparatus exhausts gas out of the chamber using an exhaust system.
As shown in FIG. 12A, the exhaust system of the substrate processing apparatus has a turbo molecular pump (hereinafter referred to as the “TMP”) 60 that is an exhausting pump capable of achieving a high vacuum state. The TMP 60 has a rotary shaft 61 that is disposed in a vertical direction as viewed in the drawing, that is, along an exhaust stream, a cylindrical main body 62 that is disposed parallel to the rotary shaft 61 such as to house the rotary shaft 61, a plurality of rotary blades 63 projecting out at right angles from the rotary shaft 61, and a plurality of stationary blades 64 projecting out from an inner peripheral surface of the main body 62 toward the rotary shaft 61. The rotary blades 63 rotate about the rotary shaft 61 at high speed, whereby gas in front of the rotary blades 63 is exhausted to the rear of the rotary blades 63 at high speed. The exhaust system exhausts gas out of the chamber by operating the TMP 60 (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. 2007-180467).
The gas exhausted out of the chamber by the exhaust system (hereinafter referred to as the “exhaust gas”) contains a highly-reactive gas and particles, and hence when the exhaust gas passes through the interior of the TMP 60, foreign matter P is deposited on or becomes attached to an internal surface of the TMP 60. Specifically, the highly-reactive gas deposits reaction product on the internal surface of the TMP 60 when passing through the interior of the TMP 60, and the particles in the exhaust gas collide with and become attached to the internal surface of the TMP 60. When the foreign matter P is deposited on or becomes attached to the internal surface of the TMP 60, an exhaust space S2 becomes smaller than a normal exhaust space S1, as shown in FIG. 12B, and hence the exhausting ability of the TMP 60 decreases.
Moreover, the foreign matter P deposited on or attached to the internal surface of the TMP 60 emits gas, and hence the TMP 60 exhausts the gas emitted from the foreign matter P as well as the gas in the chamber. Thus, the flow rate of the gas exhausted out of the chamber relatively decreases, and hence the exhausting ability of the TMP 60 for the gas in the chamber decreases.
It should be noted that when the foreign matter P separates from the internal surface of the TMP 60, it may collide with the rotary blades 63 of the TMP 60 and recoil to flow back directly into the chamber. Thus, the foreign matter P may cause particles to arise in the chamber.
Conventionally, if the exhausting ability of a TMP has decreased, the exhausting ability of the TMP is restored by detaching the TMP from the exhaust system and replacing it with a new TMP.
However, because the replacing operation takes much time, the substrate processing apparatus has to be stopped for a long time, resulting in the productivity of the substrate processing apparatus decreasing.